Session小案例-----简单购物车的使用

Session小案例-----简单购物车的使用

同上篇一样，这里的处理请求和页面显示相同用的都是servlet.

功能实现例如以下：

1，显示站点的全部商品

2。用户点击购买后，可以记住用户选择的商品

3，实现了多个会话共享一个session

4, 实现了浏览器禁用cookie后数据共享问题的处理

首页：

package cn.itcast.shopping;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//首页。显示站点全部商品
public class IndexServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html;charset=UTF-8");
		response.setCharacterEncoding("UTF-8");
		PrintWriter  out = response.getWriter();

		//为了用户第一次訪问
		request.getSession();

		//1.显示站点全部商品
		out.print("本站点有例如以下书籍：<br/>");
		Map<String,Book> map = DB.getMap();
		for(Map.Entry<String, Book> entry : map.entrySet()){
			Book book = entry.getValue();
			String url = "/day07/servlet/BuyServlet?id="+book.getId();
			url = response.encodeURL(url);  //得到重写后的url
			out.print(book.getName() + "<a href='"+url+"'>购买</a><br/>");
		}

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

class DB{
	private static Map<String,Book> map = new HashMap();
	static{
		map.put("1", new Book("1","javaweb开发","老张"));
		map.put("2", new Book("2","jdbc开发","老黎"));
		map.put("3", new Book("3","struts2开发","老张"));
		map.put("4", new Book("4","spring开发","老黎"));
		map.put("5", new Book("5","hibernate开发","老张"));
	}

	public static Map getMap(){
		return map;
	}

}

class Book implements Serializable{
	private String id;
	private String name;
	private String author;

	public Book() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Book(String id, String name, String author) {
		super();
		this.id = id;
		this.name = name;
		this.author = author;
	}
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAuthor() {
		return author;
	}
	public void setAuthor(String author) {
		this.author = author;
	}
}

购买页面：

package cn.itcast.shopping;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
//购买
public class BuyServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		//1.得到用户想买的书
		String id = request.getParameter("id");
		Book book = (Book) DB.getMap().get(id);

		//2.把用户买的书加在session中用于管理全部书的集合中了
		HttpSession session = request.getSession();

		//覆盖server的JSESSIONID的cookie
		Cookie cookie = new Cookie("JSESSIONID",session.getId());
		cookie.setMaxAge(30*60);
		cookie.setPath("/day07");
		response.addCookie(cookie);

		List list = (List) session.getAttribute("list");
		if(list==null){
			list = new ArrayList();
			session.setAttribute("list", list);
		}
		list.add(book);

		//3.跳转到购物车显示列表
		//request.getRequestDispatcher("/servlet/ListCartServlet").forward(request, response);

		//自己主动带上session的ID号
		String url  = response.encodeRedirectURL("/day07/servlet/ListCartServlet");    //实现 url重写
		response.sendRedirect(url);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

购物车列表显示页面：

package cn.itcast.shopping;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//显示用户买的全部书（购物车列表显示页面）
public class ListCartServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html;charset=UTF-8");
		response.setCharacterEncoding("UTF-8");
		PrintWriter  out = response.getWriter();
		out.print("您购买了例如以下商品:<br/>");

		//先推断浏览器有没以cookie的形式带sessionID过来。假设没有则推断URL地址有没有带sessionID
		List<Book> list = (List) request.getSession().getAttribute("list");
		for(Book book : list){
			out.print(book.getName() + "<br/>");
		}
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}